1. Field of the Invention
The present invention relates to an analog circuit controller and particularly a controller for controlling a plurality of analog circuits in an analog IC through two different analog signals.
2. Description of the Prior Art
TV receivers and audio instruments may control an IC for processing analog signals through control signals from a microcomputer. In a TV receiver, for example, commands from a TV viewer which are indicative of tint, color density and others, in television signals, may be temporarily taken by a micro computer and then applied from the microcomputer to an analog IC.
One of such controllers is shown in FIG. 1. It comprises a microcomputer 1 including a plurality of PWM (Pulse Width Modulation) circuits 2-4 located therewithin and integrating circuits 5-7 for converting the modulated pulses from the PWM circuits into analog signals which are in turn applied to circuits to be controlled 9-11 in an analog IC (8). However, the controller of FIG. 1 requires one control line for every control function to be carried out. If the number of pins in the microcomputer and IC is increased, the wiring in such a controller will become undesirably complicated.
To overcome such a problem, there has been proposed a method of time dividing digital signals and transmitting the divided digital signal through clock and data lines, as shown in FIG. 2. Digital data are applied from a microcomputer 1 to an analog IC 8 in synchronism with clock signals. The analog IC 8 includes an address control circuit 12 for decoding the incoming digital data and for judging which circuit to be controlled the data are to be transmitted to, so that the digital data will be distributed to an appropriate circuit to be controlled. The digital data are converted into analog signals through D/A conversion circuits 13-15 before they are applied to circuits to be controlled 9-11.
The method of FIG. 2 can transmit different types of control signals through only two signal lines. However, the method of FIG. 2 requires a plurality of D/A conversion circuits 13-15 in the analog IC 8. In general, an analog IC having many D/A conversion circuits, each of which is also formed having an increased number of elements, raises a problem in that the chip area increases.
On the other hand, the microcomputer 1 is formed by MOSIC and therefore does not raise any problem even if there are many D/A conversion circuits. It is therefore desired that a transmission process for performing the D/A conversion in the microcomputer using less signal lines is provided.